Unsaturated compounds have carbon-carbon double bonds. These compounds exist in either the cis or the trans configuration. Specifically unsaturated compounds having functional groups having C═O are technically very important and have different properties depending on which double bond isomer (cis or trans) is present in the corresponding compound. These compounds are particularly important for the fields of flavours and fragrances, pharmaceutical compositions and the synthesis of vitamins, particularly of vitamin K1 as well as tocopherols. The isomers particularly differ in odour as well as in their behaviour towards asymmetric additions to the respective carbon-carbon double bond.
It is known that carbon-carbon double bonds can be isomerized. Transition metal derivatives as well as sulphur compounds such as sulphides or disulfides or monomercaptanes are known to isomerize farnesol as described for example in DE 25 57 837.
U.S. Pat. No. 4,028,385 discloses transition metal catalysts as well as organic sulphur compounds such as sulphides or disulfides or monomercaptanes for the isomerization isomerize of farnesylacetic acids and esters as well as rectification of the corresponding stereoisomeric mixtures.
However, it has been observed that the organic sulphur compounds disclosed by the state of the art are not very efficient for the unsaturated compounds being selected from the group consisting of unsaturated ketones, unsaturated ketals, unsaturated aldehydes, unsaturated acetals, unsaturated carboxylic acids, esters of an unsaturated carboxylic acid and amides of an unsaturated carboxylic acid.